I think what Arkarian means is that it would be hard to take a 2D map and build a 3D map out of it. And I think he's wrong. Look at Sonic Adventure 2: Battle. If you got all the emblems (FREAKING IMPOSSIBLE I'M MISSING 2 YAR), you'd be treated to a 3D version of the first Sonic level ever. It was supposed to be, like, a reward for you suiciding over the game. And the level was actually pretty cool (friend's AR allowed me to see it). It just wasn't worth the effort.
A remake of RoS would be cool, if it wouldn't just be a coloured version of the game. I think there would have to be some cutscenes for example to tell the story, which the original RoS doesn't really deal with. You'll just bump into the game without knowing what's it about, if you haven't read the story from the manual.